Potent 1,2,4-Triazino[5,6 b]indole-3-thioether Inhibitors of the Kanamycin Resistance Enzyme Eis from Mycobacterium tuberculosis

Huy X. Ngo, Keith D. Green, Chathurada S. Gajadeera, Melisa J. Willby, Selina Y.L. Holbrook, Caixia Hou, Atefeh Garzan, Abdelrahman S. Mayhoub, James E. Posey, Oleg V. Tsodikov, Sylvie Garneau-Tsodikova

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


A common cause of resistance to kanamycin (KAN) in tuberculosis is overexpression of the enhanced intracellular survival (Eis) protein. Eis is an acetyltransferase that multiacetylates KAN and other aminoglycosides, rendering them unable to bind the bacterial ribosome. By high-throughput screening, a series of substituted 1,2,4-triazino[5,6b]indole-3-thioether molecules were identified as effective Eis inhibitors. Herein, we purchased 17 and synthesized 22 new compounds, evaluated their potency, and characterized their steady-state kinetics. Four inhibitors were found not only to inhibit Eis in vitro, but also to act as adjuvants of KAN and partially restore KAN sensitivity in a Mycobacterium tuberculosis KAN-resistant strain in which Eis is upregulated. A crystal structure of Eis in complex with a potent inhibitor and CoA shows that the inhibitors bind in the aminoglycoside binding site snugly inserted into a hydrophobic cavity. These inhibitors will undergo preclinical development as novel KAN adjuvant therapies to treat KAN-resistant tuberculosis.

Original languageEnglish
Pages (from-to)1030-1040
Number of pages11
JournalACS Infectious Diseases
Issue number6
StatePublished - Jun 8 2018

Bibliographical note

Funding Information:
This study was funded by a National Institutes of Health (NIH) Grant No. AI090048 (to S.G.-T.), a grant from the Firland Foundation (to S.G.-T.), and a grant from the Center for Chemical Genomics (CCG) at the University of Michigan (to S.G.-T.), as well as by startup funds from the College of Pharmacy at the University of Kentucky (to S.G.-T. and O.V.T). H.X.N. was in part supported by a Pharmaceutical Sciences Excellence in Graduate Achievement Fellowship from the College of Pharmacy at the University of Kentucky. We thank S. Vander Roest, M. Larsen, and P. Kirchhoff from the CCG at the University of Michigan for their help with HTS. We thank the staff of sector 22 (SER-CAT) of the Advanced Photon Source at the Argonne National Laboratories for their assistance with the remote X-ray diffraction data collection. The beamline use was supported, in part, by the Center for Structural Biology at the University of Kentucky. We thank Dr. Wenjing Chen for preliminary work on IC50 value determination. We thank Helen V. Waldschmidt and Matthew D. Demars for the help in the preliminary synthesis of a few molecules. Use of trade names is for identification only and does not constitute endorsement by the U.S. Department of Health and Human Services, the U.S. Public Health Service, or the CDC. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the funding agencies.

Publisher Copyright:
© 2018 American Chemical Society.


  • aminoglycoside resistance
  • antitubercular agent
  • combination therapy
  • high-throughput screen
  • structure-activity relationship (SAR)

ASJC Scopus subject areas

  • Infectious Diseases


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